Driver instruments and related methods

ABSTRACT

Driver instruments are disclosed herein with various features for improving usability, easing the task of cleaning or sterilizing the instrument, reducing patient trauma associated with use of the instrument, and/or reducing the cost and assembly burden of the instrument. For example, a driver instrument can include a guide sleeve to protect patient tissue from damage caused by rotating components of the instrument or a bone anchor assembly coupled thereto, and to protect extension tabs of the bone anchor assembly from inadvertent separation. By way of further example, an instrument can include a preload assembly for maintaining engagement of a driver shaft of the instrument with a bone anchor assembly. As yet another example, an instrument can consist of a small number of components which are configured for simple, tool-free assembly and disassembly. An instrument can also be configured for use with bone anchor assemblies with and without extension tabs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/685,454, filed Apr. 13, 2015, and entitled “Driver Instruments andRelated Methods.” This application is hereby incorporated by referencein its entirety.

FIELD

Driver instruments and related methods for driving bone anchorassemblies into bone are disclosed herein.

BACKGROUND

Bone anchors can be used in orthopedic surgery to fix bone duringhealing, fusion, or other processes. In spinal surgery, for example,bone anchors can be used to secure a spinal fixation element to one ormore vertebrae to rigidly or dynamically stabilize the spine.

In a conventional procedure for coupling a bone anchor to bone, accessto the bone is obtained, for example by forming a skin incision andresecting soft tissue disposed over the bone or by using aminimally-invasive technique. A guidewire is partially inserted into thebone to establish the trajectory for the bone anchor. The bone anchor isthen advanced over the guidewire and rotationally driven into the boneusing a driver instrument. The guidewire is then removed and one or morefixation elements are coupled to the bone anchor.

While a number of driver instruments have been developed for advancingbone anchors into bone, there is a continual need for improved driverinstruments and related methods of driving bone anchors.

SUMMARY

Driver instruments are disclosed herein with various features forimproving usability, easing the task of cleaning or sterilizing theinstrument, reducing patient trauma associated with use of theinstrument, and/or reducing the cost and assembly burden of theinstrument. For example, a driver instrument can include a guide sleeveto protect patient tissue from damage caused by rotating components ofthe instrument or a bone anchor assembly coupled thereto, and to protectextension tabs of the bone anchor assembly from inadvertent separation.By way of further example, an instrument can include a preload assemblyfor maintaining engagement of a driver shaft of the instrument with abone anchor assembly. As yet another example, an instrument can consistof a small number of components which are configured for simple,tool-free assembly and disassembly. An instrument can also be configuredfor use with bone anchor assemblies with and without extension tabs.

In some embodiments, an instrument for driving a bone anchor assemblyinto bone includes a driver shaft having a distal drive tip and aproximal driven end; an elongate body having proximal and distal endsthat defines a central passage in which the driver shaft is rotatablydisposed; and a release button disposed in the body and having at leasta first position in which the driver shaft can be removed from the bodyand a second position in which the driver shaft cannot be removed fromthe body.

The instrument can include a preload assembly configured to bias thedriver shaft in a distal direction relative to the body. In someembodiments, a location at which the preload assembly engages the drivershaft can be selected from amongst a plurality of locations to adjustthe degree to which the driver shaft protrudes from the distal end ofthe body. The plurality of locations can be defined by radialprojections that extend from the driver shaft. The instrument caninclude a guide sleeve positionable over a distal end of the body andconfigured to separate the body and the driver shaft from surroundingtissue when the instrument is used to drive a bone anchor assembly intobone. The sleeve can include a flared distal end and a flared proximalend. The sleeve can include a lever configured to pivot at a fulcrumpoint to selectively engage and disengage the sleeve with the body. Thelever can be formed integrally with the sleeve at a living hinge. Thesleeve can be rotatable with respect to the body and with respect to thedriver shaft. The sleeve can be configured to engage any of a pluralityof mating features spaced longitudinally along the body. The body caninclude an engagement portion formed at a distal end thereof, theengagement portion being configured to engage a corresponding engagementportion on a bone anchor assembly. The release button can be disposed ina housing portion of the body, the housing portion having a plurality ofopenings through which fluid can access the central passage. The releasebutton can include a cylindrical recess in which a sliding collar isdisposed, the driver shaft extending through the sliding collar. Thesliding collar can include a plurality of openings spaced about asidewall thereof. The instrument can include a preload spring disposedbetween the collar and the release button.

In some embodiments, an instrument for driving a bone anchor assemblyinto bone includes a driver shaft having a distal drive tip and aproximal driven end; an elongate body having proximal and distal endsthat defines a central passage in which the driver shaft is rotatablydisposed; a release button disposed in the body and having a collarslidably disposed therein, the collar being configured to selectivelyengage the driver shaft; and a preload spring disposed between therelease button and the collar configured to bias the driver shaft in adistal direction with respect to the body.

The driver shaft can include a plurality of projections extendingradially outward therefrom, and the degree to which the driver shaftprotrudes from the distal end of the body can be adjusted by selectingwhich of the plurality of projections engages the collar.

In some embodiments, a method of driving a bone anchor assembly intobone includes engaging a drive interface of a bone anchor assembly witha drive tip of a driver shaft; advancing a body portion in which thedriver shaft is rotatably disposed distally with respect to the boneanchor assembly to couple an engagement feature of the body portion witha corresponding engagement feature of the bone anchor assembly, whereinsaid distal advancement preloads a spring disposed in the body portion;rotating the driver shaft to drive the bone anchor assembly into bone;and actuating a release button to disengage the driver shaft from thebody portion such that the driver shaft can be removed from the bodyportion.

The method can include positioning a guide sleeve disposed over the bodyportion between extension tabs of the bone anchor assembly andsurrounding tissue. The method can include selecting from amongst aplurality of positions at which the driver shaft can be engaged by thebody portion to adjust a degree to which the driver shaft protrudes froma distal end of the body portion.

The present invention further provides devices and methods as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1A is an exploded perspective view of a prior art bone anchorassembly;

FIG. 1B is a sectional view of the prior art bone anchor assembly ofFIG. 1A;

FIG. 2 is a perspective view of a driver instrument;

FIG. 3 is an exploded perspective view of the driver instrument of FIG.2;

FIG. 4 is a sectional view of the driver instrument of FIG. 2;

FIG. 5 is an exploded perspective view of a body portion of the driverinstrument of FIG. 2;

FIG. 6 is a sectional view of the body portion of the driver instrumentof FIG. 2;

FIG. 7 is a perspective view of a release button of the driverinstrument of FIG. 2;

FIG. 8 is a sectional view of the driver instrument of FIG. 2 with therelease button in a released position;

FIG. 9 is a sectional view of the driver instrument of FIG. 2 with therelease button in an engaged position;

FIG. 10 is a sectional view of the driver instrument of FIG. 2 coupledto a bone anchor assembly before a preload assembly is loaded;

FIG. 11 is a sectional view of the driver instrument of FIG. 2 coupledto a bone anchor assembly after the preload assembly is loaded;

FIG. 12 is a perspective view of a driver instrument;

FIG. 13 is an exploded perspective view of the driver instrument of FIG.12; and

FIG. 14 is a sectional view of the driver instrument of FIG. 12.

DETAILED DESCRIPTION

Driver instruments are disclosed herein with various features forimproving usability, easing the task of cleaning or sterilizing theinstrument, reducing patient trauma associated with use of theinstrument, and/or reducing the cost and assembly burden of theinstrument. For example, a driver instrument can include a guide sleeveto protect patient tissue from damage caused by rotating components ofthe instrument or a bone anchor assembly coupled thereto, and to protectextension tabs of the bone anchor assembly from inadvertent separation.By way of further example, an instrument can include a preload assemblyfor maintaining engagement of a driver shaft of the instrument with abone anchor assembly. As yet another example, an instrument can consistof a small number of components which are configured for simple,tool-free assembly and disassembly. An instrument can also be configuredfor use with bone anchor assemblies with and without extension tabs.

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those of skilled in the art will understand that the devicesand methods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

Prior Art Bone Anchor Assembly

FIGS. 1A-1B illustrate a prior art bone anchor assembly 10 that includesa bone anchor 12, a receiver member 14 for receiving a spinal fixationelement, such as a spinal rod 22, to be coupled to the bone anchor 12,and a closure mechanism 16 to capture a spinal fixation element withinthe receiver member 14 and fix the spinal fixation element with respectto the receiver member 14. The bone anchor 12 includes a proximal head18 and a distal shaft 20 configured to engage bone. The receiver member14 has a proximal end 26 having a pair of spaced apart arms 28A, 28Bdefining a recess 30 therebetween and a distal end 32 having a distalend surface 34 defining an opening through which at least a portion ofthe bone anchor 12 extends. The closure mechanism 16 can be positionablebetween and can engage the arms 28A, 28B to capture a spinal fixationelement, e.g., a spinal rod 22, within the receiver member 14 and fixthe spinal fixation element with respect to the receiver member 14.

The proximal head 18 of the bone anchor 12 is generally in the shape ofa truncated sphere having a planar proximal surface 36 and anapproximately spherically-shaped distal surface 38. The illustrated boneanchor assembly is a polyaxial bone screw designed for posteriorimplantation in the pedicle or lateral mass of a vertebra. The proximalhead 18 of the bone anchor 12 engages the distal end 32 of the receivermember 14 in a ball and socket like arrangement in which the proximalhead 18 and the distal shaft 20 can pivot relative to the receivermember 14. The distal surface 38 of the proximal head 18 of the boneanchor 12 and a mating surface within the distal end 32 of the receivermember 14 can have any shape that facilitates this arrangement,including, for example, spherical (as illustrated), toroidal, conical,frustoconical, and any combinations of these shapes.

The distal shaft 20 of the bone anchor 12 can be configured to engagebone and, in the illustrated embodiment, includes an external boneengaging thread 40. The thread form for the distal shaft 20, includingthe number of threads, the pitch, the major and minor diameters, and thethread shape, can be selected to facilitate connection with bone.Exemplary thread forms are disclosed in U.S. Patent ApplicationPublication No. 2011/0288599, filed on May 18, 2011, and in U.S. PatentApplication Publication No. 2013/0053901, filed on Aug. 22, 2012, bothof which are hereby incorporated by reference herein. The distal shaft20 can also include other structures for engaging bone, including ahook. The distal shaft 20 of the bone anchor 12 can be cannulated,having a central passage or cannula 72 extending the length of the boneanchor to facilitate delivery of the bone anchor over a guidewire in,for example, minimally-invasive procedures. Other components of the boneanchor assembly 10, including, for example, the closure mechanism 16,the receiver member 14, and the compression member 60 (discussed below)can be cannulated or otherwise have an opening to permit delivery over aguidewire. The distal shaft 20 can also include one or more sidewallopenings or fenestrations that communicate with the cannula to permitbone in-growth or to permit the dispensing of bone cement or othermaterials through the bone anchor 12. The sidewall openings can extendradially from the cannula through the sidewall of the distal shaft 20.Exemplary systems for delivering bone cement to the bone anchor assembly10 and alternative bone anchor configurations for facilitating cementdelivery are described in U.S. Patent Application Publication No.2010/0114174, filed on Oct. 29, 2009, which is hereby incorporated byreference herein. The distal shaft 20 of the bone anchor 12 can also becoated with materials to permit bone growth, such as, for example,hydroxyapatite, and the bone anchor assembly 10 can be coated partiallyor entirely with anti-infective materials, such as, for example,tryclosan.

The proximal end 26 of the receiver member 14 includes a pair of spacedapart arms 28A, 28B defining a U-shaped recess 30 therebetween forreceiving a spinal fixation element, e.g., a spinal rod 22. Each of thearms 28A, 28B can extend from the distal end 32 of the receiver member14 to a free end. The outer surfaces of each of the arms 28A, 28B caninclude a feature, such as a recess, dimple, notch, projection, or thelike, to facilitate connection of the receiver member 14 to instruments.For example, the outer surface of each arm 28A, 28B can include anarcuate groove at the respective free end of the arms. Such grooves aredescribed in more detail in U.S. Pat. No. 7,179,261, issued on Feb. 20,2007, which is hereby incorporated by reference herein.

The distal end 32 of the receiver member 14 includes a distal endsurface 34 which is generally annular in shape defining a circularopening through which at least a portion of the bone anchor 12 extends.For example, the distal shaft 20 of the bone anchor 12 can extendthrough the opening.

The bone anchor 12 can be selectively fixed relative to the receivermember 14. Prior to fixation, the bone anchor 12 is movable relative tothe receiver member 14 within a cone of angulation generally defined bythe geometry of the distal end 32 of the receiver member and theproximal head 18 of the bone anchor 12. The bone anchor 10 can be afavored angle screw, for example as disclosed in U.S. Pat. No.6,974,460, issued on Dec. 13, 2005, and in U.S. Pat. No. 6,736,820,issued on May 18, 2004, both of which are hereby incorporated byreference herein. Alternatively, the bone anchor assembly can be aconventional (non-biased) polyaxial screw in which the bone anchorpivots in the same amount in every direction.

The spinal fixation element, e.g., the spinal rod 22, can eitherdirectly contact the proximal head 18 of the bone anchor 12 or cancontact an intermediate element, e.g., a compression member 60. Thecompression member 60 can be positioned within the receiver member 14and interposed between the spinal rod 22 and the proximal head 18 of thebone anchor 12 to compress the distal outer surface 38 of the proximalhead 18 into direct, fixed engagement with the distal inner surface ofthe receiver member 14. The compression member 60 can include a pair ofspaced apart arms 62A and 62B defining a U-shaped seat 64 for receivingthe spinal rod 22 and a distal surface 66 for engaging the proximal head18 of the bone anchor 12.

The proximal end 26 of the receiver member 14 can be configured toreceive a closure mechanism 16 positionable between and engaging thearms 28A, 28B of the receiver member 14. The closure mechanism 16 can beconfigured to capture a spinal fixation element, e.g., a spinal rod 22,within the receiver member 14, to fix the spinal rod 22 relative to thereceiver member 14, and to fix the bone anchor 12 relative to thereceiver member 14. The closure mechanism 16 can be a single set screwhaving an outer thread for engaging an inner thread 42 provided on thearms 28A, 28B of the receiver member 14. In other embodiments, however,the closure mechanism 16 can include an outer set screw operable to acton the compression member 60 and an inner set screw operable to act onthe rod 22. The receiver member 14 can include or can be coupled to oneor more extension tabs (not shown) that extend proximally from thereceiver member 14 to functionally extend the length of the arms 28A,28B. The extension tabs can facilitate installation and assembly of afixation or stabilization construct and can be removed prior tocompleting a surgical procedure.

The bone anchor assembly 10 can be used with a spinal fixation elementsuch as rigid spinal rod 22. Alternatively, the spinal fixation elementcan be a dynamic stabilization member that allows controlled mobilitybetween the instrumented vertebrae.

In use, the bone anchor assembly 10 can be assembled such that thedistal shaft 20 extends through the opening in the distal end 32 of thereceiver member 14 and the proximal head 18 of the bone anchor 12 isreceived in the distal end 32 of the receiver member 14. A driverinstrument can be fitted with the bone anchor 12 to drive the boneanchor 12 into bone. The compression member 60 can be positioned withinthe receiver member 14 such that the arms 62A, 62B of the compressionmember are aligned with the arms 28A, 28B of the receiver member 14 andthe lower surface of the compression member 14 is in contact with theproximal head 18 of the bone anchor 12. A spinal fixation element, e.g.,the spinal rod 22, can be located in the recess 30 of the receivermember 14. The closure mechanism 16 can be engaged with the inner thread42 provided on the arms 28A, 28B of the receiver member 14. A torsionalforce can be applied to the closure mechanism 16 to move it within therecess 30 so as to force the spinal rod 22 into engagement with thecompression member 60 and to in turn force the compression member 60onto the proximal head 18 of the bone anchor 12, thereby fixing thespinal rod 22 relative to the receiver member 14 and locking the angularposition of the bone anchor 12 relative to the receiver member 14.

The driver instruments disclosed herein can be configured to operate inconjunction with bone anchor assemblies of the type described above orother types known in the art. Exemplary bone anchor assemblies includemonoaxial screws, polyaxial screws, uniplanar screws, favored-anglescrews, and/or any of a variety of other bone anchor types known in theart. Further information on favored-angle screws can be found in U.S.Patent Application Publication No. 2013/0096618, filed on Oct. 9, 2012,which is hereby incorporated by reference herein. Bone anchor assembliesare sometimes referred to herein simply as “bone anchors.”

Driver Instruments and Related Methods

FIGS. 2-11 illustrate an exemplary embodiment of a driver instrument 200for driving a bone anchor assembly. The driver instrument 200 can alsobe used to drive a bone tap or any other rotationally-driven element.The instrument 200 generally includes a driver shaft 202, a guide sleeve204, and a body 206. The body 206 can define a central passage throughwhich the driver shaft 202 is received and in which the driver shaft canrotate relative to the body. A distal portion of the body 206 can bereceived within a central passage of the guide sleeve 204 such that thebody is rotatable with respect to the guide sleeve.

As shown in FIG. 3, the driver shaft 202 can include an elongatecylindrical body having a proximal end 202 p and a distal end 202 d andextending along a central longitudinal axis L1. The body of the drivershaft 202 can be cannulated to allow passage of a guidewiretherethrough. The cannulation can also allow for injection of bonecement or other flowable materials through the driver shaft 202 to abone anchor assembly coupled thereto.

The proximal end 202 p of the driver shaft 202 can include a modularcoupling 208 for selectively attaching the driver shaft to a structureor device for applying a rotational force to the driver shaft about thelongitudinal axis L1. For example, the modular coupling 208 can beconfigured to attach the driver shaft 202 to a handle or knob configuredto be grasped by a user, to a powered device such as an electric orpneumatic drill or driver, or to a surgical robot. In other embodiments,the driver shaft 202 can include a handle formed integrally therewith.

The distal end 202 d of the driver shaft 202 can include a drive tip 210for engaging a corresponding drive interface of a bone anchor and fortransferring rotational force applied to the driver shaft to the boneanchor. Exemplary drive tips include Phillips, slotted, hexalobe, Torx®,hexagonal, pentalobe, and the like, of various standard or non-standardsizes. The drive tip 210 can also include a modular connector such thatany of a plurality of drive tips having different types or sizes can beselectively coupled to the distal end of the driver shaft 202.

The driver shaft 202 can also include one or more radial projections orprotrusions to facilitate interaction with various components of thebody 206, as detailed below. In the illustrated embodiment, the drivershaft 202 includes proximal and distal radial projections 212, 214. Theproximal projection 212 can include proximal-facing and distal-facingsurfaces that extend substantially perpendicular to the driver shaft202. The distal projection 214 can include a proximal-facing surfacethat is substantially perpendicular to the driver shaft 202 and adistal-facing surface that extends from the driver shaft at an obliqueangle.

As shown in FIGS. 3-4, the guide sleeve 204 can include an elongatetubular frame having a proximal end 204 p and a distal end 204 d andextending along a central longitudinal axis L2. One or both ends of thesleeve 204 can be flared or enlarged such that the end has a diametergreater than that of the central portion of the sleeve. For example, thesleeve 204 can have a flared proximal portion 216 sized to accommodate acorresponding flared portion of the body 206. The flared proximalportion 216 can provide an indication to a user as to the properorientation of the sleeve 204 with respect to the body 204 duringassembly of the instrument 200. By way of further example, the sleeve204 can have a flared distal portion 218 to guide or facilitateinsertion of at least a portion of a bone anchor assembly therein. Inother words, the flared distal portion 218 can act as a funnel orlead-in for the proximal end of a bone anchor assembly as it is insertedinto the distal end of the sleeve 204.

The sleeve 204 can also include one or more mating features for couplingthe sleeve to the body 206. In the illustrated embodiment, the matingfeatures include first and second tabs or projections 220 that extendradially-inward towards the central axis L2 of the sleeve 204. The tabs220 can be configured to engage corresponding grooves, recesses, orother mating features formed on the body, as discussed further below.The tabs 220 can extend from respective lever arms 222 which can bepivoted with respect to the sleeve 204 to move the tabs radially inwardtowards the central passage of the sleeve or radially outward away fromthe central passage of the sleeve. A leading proximal edge of the tabs220 can be chamfered to allow the tabs to cam over the exterior of thebody 206 until they snap into a recess or groove formed in the body.

Each lever arm 222 can be a separate component from the sleeve 204, orcan be formed integrally with the sidewall of the sleeve as shown, e.g.,by removing material from the sleeve to define an outline of the leverarm. A small section of material can be left on each lateral side of thelever arm 222 to define a living hinge 224 that acts as a fulcrum forthe lever arm. While removal of material from the sleeve 204 isgenerally described herein, it will be appreciated that the lever arms222 can be formed by addition of material to the sleeve, by molding, orby other processes which will be apparent to one skilled in the art. Aportion of the lever arm 222 disposed opposite the fulcrum 224 from theportion of the lever arm from which the tab 220 extends can serve as abutton 226 which, when depressed by a user, causes the tab to moveradially outward and disengage the body 206. The material used to formthe fulcrum 224 can have resilient properties such that, when the buttonportion 226 of the lever arm 222 is released by the user, the tabs 220can be biased radially inward back towards a position in which theyengage the body 206. Other biasing elements, such as coiled or leafsprings, can be included instead or in addition.

As shown in FIG. 5, the body 204 can extend along a central longitudinalaxis L3 and can include a distal stem portion 228 and a proximal housing230 in which a release button and preload assembly are disposed. Thestem portion 228 and the proximal housing 230 can collectively define acontinuous passage 232 (shown in FIG. 6) through the body 206 in whichthe driver shaft 202 can be received. Depending on the operatingconfiguration of the instrument 200, the driver shaft 202 can beconfigured to rotate and/or translate longitudinally in variousdirections within the passage 232. The stem portion 228 of the body 206can be sized and configured to be received within the central passage ofthe sleeve 204. When the instrument is fully-assembled, the centrallongitudinal axis L1 of the driver shaft 202 can be collinear with thecentral longitudinal axis L2 of the sleeve 204 and the centrallongitudinal axis L3 of the body 206.

The distal tip of the stem portion 228 can include an engagement featureconfigured to engage at least a portion of a bone anchor assembly. Forexample, the distal tip can include an external thread 234 as shown thatis sized and configured to engage a corresponding internal thread formedin the receiver member of a bone anchor assembly, or an internal threadformed in one or more extension tabs or tubes extending proximally fromthe receiver member. It will be appreciated that various otherengagement features can be used instead or in addition.

The stem portion 228 can include one or more protrusions, bulges, orother areas of increased diameter 236 configured to support theextension tabs of a bone anchor assembly when the distal tip is engagedwith the bone anchor assembly. Such protrusions 236 can help prevent theextension tabs from bending inward towards the body 206 and breaking offor separating from the bone anchor assembly prematurely.

The proximal end of the stem portion 228 can include one or more matingfeatures to which the sleeve 204 can be coupled. In the illustratedembodiment, the stem portion 228 includes first and second grooves 238,240 that extend entirely around the outer circumference of the stemportion. It will be appreciated, however, that any number of matingfeatures of various types can be used instead or in addition. The firstand second grooves 238, 240 can be sized to receive the tabs 220 of thesleeve 204 therein to maintain the sleeve and the body 206 at a fixedlongitudinal position with respect to one another while permitting thesleeve and the body to rotate with respect to one another. Thelongitudinal position of the sleeve 204 relative to the body 206 can beadjusted by changing which of the grooves 238, 240 is engaged by thetabs 220. For example, when the tabs 220 are disposed in the firstgroove 238, the distal end of the sleeve 204 can extend down over thereceiver member of a bone anchor assembly coupled to the body 206. Whenthe tabs 220 are disposed in the second groove 240, the distal end ofthe sleeve 204 can be retracted, e.g., such that the mating interfacebetween the body 206 and the bone anchor assembly is disposed outside ofthe sleeve and able to be visualized or handled by a user. Differentgrooves can also be selected depending on the type of bone anchorassembly being used with the driver instrument 200 (e.g., based onwhether or not the bone anchor assembly includes extension tabs).

The mating features 238, 240 can be formed at any longitudinal positionalong the body, however in the illustrated embodiment they are formed ina flared proximal portion 242. The flared proximal portion 242 has anoutside diameter that is greater than the outside diameter of the distalportion of the stem 228 such that the flared portion corresponds to theflared portion 216 of the sleeve 204.

The proximal housing 230 of the body 206 can include a release button244 with a corresponding button spring 246 and a locking pin 248. Thehousing 230 can also include a preload assembly. In the illustratedembodiment, the preload assembly includes a sliding collar 250 and apreload spring 252.

The housing 230 can define a chamber 254 that is open to a sidewall ofthe housing and that intersects with the central passage 232 of the body206. The chamber 254 can be sized and shaped to correspond to the sizeand shape of the release button 244, and to slidably receive the releasebutton therein such that the release button can move within the chambertowards and away from the central passage 232. One or more openings 256can be formed in the sidewall of the housing 230, which canadvantageously allow sterilizing solutions, cleaning agents, or otherflowable materials to access the interior of the housing. In theillustrated embodiment, the housing 230 includes a faceted sidewall,with each face including at least one opening 256 formed therein. Inaddition, the proximal end surface 258 of the housing 230 can becompletely open to allow further access to the interior of the housing.The housing 230 can also include one or more longitudinal grooves 260 tomake the housing easier to grip.

The release button 244 can include a substantiallyrectangular-parallelepiped body having proximal and distal surfaces 244p, 244 d. A cylindrical opening 262 can be formed through the button244, extending between the proximal and distal surfaces. As shown inFIG. 7, an annular flange 264 can extend inward into the cylindricalopening 262 to define a proximal seat for the preload spring 252.

The sliding collar 250 can include a substantially tubular body having adistal annular lip 266 that extends radially-outward from an exteriorsurface of the collar to define a distal seat for the preload spring252. The outside diameter of the lip 266 can be equal to or slightlyless than the inside diameter of the cylindrical opening 262 formed inthe release button 244 to allow the collar 250 to be received within therelease button and to slide longitudinally therein. As shown in FIG. 6,the preload spring 252 can be captured on either end between theproximal and distal seats 264, 266 and along a length thereof betweenthe interior of the release button 244 and the exterior of the collar250.

One or more openings 268 can be formed in the sidewall of the collar250, which can advantageously allow sterilizing solutions, cleaningagents, or other flowable materials to access the interior of thecollar. In the illustrated embodiment, the collar 250 includes aplurality of elongated openings 268 spaced evenly about thecircumference of the collar.

The button spring 246 can be partially received within a first bore 270formed in the bottom of the chamber 254 and partially received within asecond bore 272 formed in the sidewall of the release button 244 thatfaces the bottom of the chamber. The button spring 246 can thus beeffective to bias the release button 244 away from the bottom of thechamber 254 such that the release button is urged in a directionradially-outward from the housing 230. The locking pin 248 can extendthrough an opening 274 formed in the sidewall of the housing 230 andinto an elongated slot 276 formed in the release button 244. The lockingpin 248 can thus limit the travel of the release button 244 within thechamber 254 to prevent the release button from falling out of thehousing 230. The locking pin 248 can be welded or otherwise secured tothe housing 230 after assembly to prevent inadvertent disassembly.

The release button 244 can be slidable within the chamber 254 between atleast a first, released position (shown in FIG. 8) and a second, engagedposition (shown in FIG. 9). The button 244 can be biased towards theengaged position and can be configured to move from the engaged positionto the released position when depressed by a user.

In the released or disengaged position, as shown in FIG. 8, depressionof the button 244 moves the collar 250 out of the path of theprojections 212, 214 formed on the driver shaft 202, such that thecollar does not engage the projections and such that the collar does notrestrict longitudinal movement of the driver shaft relative to the body206. Thus, in the disengaged position, the driver shaft 202 can beindexed to a desired longitudinal position with respect to the body 206,withdrawn completely from the body, or inserted through the body toassemble the instrument 200. The driver shaft 202 can be free to rotaterelative to the body 206 when the button 244 is in the releasedposition.

In the engaged position, as shown in FIG. 9, the bias of the buttonspring 246 urges the release button 244 upwards such that a portion ofthe sidewall of the sliding collar 250 interferes with at least one ofthe projections 212, 214 of the driver shaft 202 to prevent certainlongitudinal movement of the driver shaft relative to the body 206. Forexample, in the engaged position, proximal movement of the driver shaft202 relative to the body 206 is resisted by the bias of the preloadspring 252 and eventually prevented altogether when the preload springis completely compressed. The driver shaft 202 can remain free to rotaterelative to the body 206 when the button 244 is in the engaged position.The driver shaft 202 can also be free to translate distally relative tothe body 206 when the button 244 is in the engaged position, e.g., untilone of the projections 214 of the driver shaft 202 hits a stop shoulder278 formed in the distal stem portion 228 of the body 206.

Operation of the preload assembly is illustrated further in FIGS. 10-11.When the release button 244 is in the engaged position, longitudinalmovement of the body 206 in a distal direction relative to the drivershaft 202 forces the sliding collar 250 to move proximally with respectto the release button 244, compressing the preload spring 252. In otherwords, as shown in FIG. 10, the preload spring 252 biases the slidingcollar 250 (and the driver shaft 202 when the release button 244 is inthe engaged position) distally with respect to the body 206. As thedriver instrument 200 is advanced towards a bone anchor assembly 300,the distal end 202 d of the driver shaft 202 comes into contact with thedrive interface 302 of the bone anchor assembly, preventing furtherdistal movement of the driver shaft.

Continued distal advancement of the instrument 200 towards the boneanchor assembly 300 causes the driver shaft 202 to slide proximallyrelative to the body 206, compressing the preload spring 252. As shownin FIG. 11, the relative longitudinal positions of the driver shaft 202and the body 206 can be indexed by the placement of the protrusions 212,214 such that, as the distal end 234 of the body 206 begins tothreadably engage the receiver member 304 or extension tabs 306 of thebone anchor assembly 300, the driver shaft 202 contacts the driveinterface 302 of the bone anchor assembly and begins to move proximallyand compress the preload spring 252. This preload feature canadvantageously maintain engagement between the driver shaft 202 and thebone anchor assembly 300. In particular, the preload function canmaintain the driver shaft 202 in engagement with the drive interface 302of the bone anchor assembly 300, preventing the driver shaft 202 fromslipping out of engagement as the body 206 is advanced distally withrespect to the bone anchor assembly.

The locations along the length of the driver shaft 202 at which theprotrusions 212, 214 are positioned can be selected such that eachprotrusion corresponds to a different bone anchor configuration. In theillustrated embodiment, the proximal protrusion 212 can be used as theoperative protrusion when a bone anchor assembly having extension tabsis used, such that the proximal protrusion is positioned just distal tothe collar 250. On the other hand, when a bone screw assembly withoutextension tabs is used, the distal protrusion 214 can be used as theoperative protrusion, such that the distal protrusion is positioned justdistal to the collar 250 (e.g., such that the collar is disposed betweenthe proximal and distal protrusions 212, 214).

In use, the instrument 200 can be provided initially in a completelyassembled or completely disassembled state. The instrument 200 can alsobe provided initially in a partially-assembled state (e.g., with thepreload assembly and release button 244 assembled to the body 206, butthe body not yet assembled with the driver shaft 202 and/or the sleeve204).

The driver shaft 202 can be inserted through the central passage 232 ofthe body 206 and the distal tip 202 d of the driver shaft 202 can beengaged with a drive interface of a bone anchor assembly. The releasebutton 244 can be depressed by the user to hold the button in thereleased position if necessary to allow insertion of the driver shaft202 through the body 206. As the driver shaft 202 is inserted, the usercan select the appropriate protrusion 212, 214 of the driver shaft toengage with the sliding collar 250, depending on the configuration ofthe bone anchor assembly (e.g., depending on whether or not the boneanchor assembly includes extension tabs).

With the driver shaft 202 inserted through the body 206, the body can becoupled to the receiver member or extension tabs of a bone anchorassembly, for example by threading the distal mating feature 234 of thebody into corresponding threads of the bone anchor assembly. In theprocess of coupling the bone anchor assembly to the body 206, the bodycan be advanced distally relative to the driver shaft 202, which can beprevented from itself advancing distally by the drive interface of thebone anchor assembly. As the body 206 is advanced distally, the preloadspring 252 can be compressed to generate a preload force that tends tomaintain the driver shaft 202 in contact with the bone anchor assembly.

While the driver shaft 202 is preferably inserted through the body 206prior to coupling the body to the bone anchor assembly (or when the bodyis only partially coupled to the bone anchor assembly) so as to preloadthe driver shaft, it will be appreciated that other assembly sequencesare also possible.

Before or after coupling the body 206 to the bone anchor assembly andbefore or after inserting the driver shaft 202 through the body toengage the bone anchor assembly, the guide sleeve 204 can be assembledover the distal stem 228 of the body. A user can squeeze the buttonportions 226 of the lever arms 222 together to move the tabs 220 out ofthe central passage of the sleeve 204, slide the sleeve to the desiredlongitudinal position along the stem 228, and then release the buttonsto allow the tabs to engage one of the grooves 238, 240 in the stem. Thesleeve 204 can also be assembled without squeezing the buttons 226,instead simply allowing the tabs 220 to cam over the exterior of thestem 228 until they snap into the desired groove. It will be appreciatedthat the sleeve 204 need not necessarily be used when driving the boneanchor assembly. Use of the sleeve 204, however, can provide a number ofadvantages. For example, the sleeve 204 can form a protective barrierbetween patient tissue and components which may rotate during screwinstallation, such as the extension tabs, the receiver member, or thedriver shaft 202. This can desirably prevent delicate tissue (e.g.,muscle, nerves, vasculature, connective tissue, etc.) from beingabraded, cut, tangled, or otherwise damaged by the rotating components.

With the instrument 200 assembled, the bone anchor assembly can bedriven into bone by rotating the driver shaft 202 about the longitudinalaxis L1, e.g., using manual force applied to a knob of the driver shaftor using a powered drill coupled to the driver shaft. As the bone anchorassembly advances into the bone, the driver shaft 202 can advancedistally relative to the body 206, gradually unloading the preloadspring 252. In some embodiments, the distal protrusion 214 can bepositioned such that it contacts the shoulder 278 formed in the centralpassage 232 of the body 206 to prevent over-advancement of the drivershaft 202.

When the bone anchor assembly is implanted to the target depth, or atany other time desired by a user, the instrument 200 can be decoupledfrom the bone anchor assembly. For example, the body 206 can be detachedfrom the bone anchor assembly by unthreading the body from the extensiontabs (or from the receiver member). As another example, the driver shaft202 can be detached from the bone anchor assembly by pushing the releasebutton 244 to move the collar 250 to the released position andwithdrawing the driver shaft proximally relative to the body 206.

It should be noted that any ordering of method steps expressed orimplied in the description above or in the accompanying drawings is notto be construed as limiting the disclosed methods to performing thesteps in that order. Rather, the various steps of each of the methodsdisclosed herein can be performed in any of a variety of sequences. Inaddition, as the described methods are merely exemplary embodiments,various other methods that include additional steps or include fewersteps are also within the scope of the present invention. It willfurther be appreciated that the instrument 200 can be used in a similarmanner to remove a bone anchor assembly previously implanted orpartially implanted in bone.

As evident from the foregoing, in at least some embodiments, theinstrument 200 can provide one or more advantages as compared with otherdriver instruments:

The instrument 200 can be quickly assembled or disassembled by simplebutton pushes without requiring tools or complex procedures.

The ability to rapidly assemble and disassemble the instrument 200 canfacilitate more effective, more comprehensive, and/or more expedientcleaning, sterilization, and reuse of the instrument.

The guide sleeve 204 can protect adjacent tissue from being injured ordestroyed by rotating components of the instrument 200 or bone anchorassembly.

The guide sleeve 204 can be a single piece design that reduces componentquantity and facilitates more effective, more comprehensive, and/or moreexpedient cleaning, sterilization, and reuse of the instrument 200. Thesingle piece design can also reduce the overall profile of theinstrument 200 and thus allow bone anchor insertion through asmaller-diameter cannula.

The guide sleeve 204 can be completely removable from the instrument 200to allow the instrument to be used without the guide sleeve.

The guide sleeve 204 can protect the extension tabs of a bone anchorassembly from inadvertent breakage or separation from the receivermember, for example when lateral forces are applied to the driverinstrument 200 to adjust an angle of insertion.

The guide sleeve 204 can help maintain rigid alignment between thedriver shaft 202 and the bone anchor assembly during insertion.

The openings 256 in the body housing 230 and the openings 268 in thesliding collar 250 can allow passage of cleaning solutions,sterilization fluids, and other flowable materials to facilitate moreeffective, more comprehensive, and/or more expedient cleaning,sterilization, and reuse of the instrument 200.

The openings 256 and grooves 260 in the body housing 230 can provide anenhanced gripping surface for the user. The openings 256 can also allowa crossbar to be inserted therethrough to create a T-shaped structurefor applying additional torque through the body 206.

The guide sleeve 204 and driver shaft 202 can be positioned at differentlongitudinal locations along the body 206 to allow the instrument 200 tobe used with bone anchor assemblies with and without extension tabs.

The driver shaft 202 can be completely removable from the instrument 200to allow the driver shaft to be used without the remainder of theinstrument (e.g., to fine tune the insertion depth of the bone anchorassembly after initial placement).

The instrument 200 can provide a preload function to maintain contactbetween the driver shaft 202 and the bone anchor assembly duringinsertion or removal.

FIGS. 12-14 illustrate another exemplary embodiment of a driverinstrument 400. Except as indicated below and as will be readilyapparent to one having ordinary skill in the art, the structure andoperation of the driver instrument 400 is substantially similar to thatof the driver instrument 200, and therefore a detailed description isomitted here for the sake of brevity. The driver instrument 400 caninclude a guide sleeve 404 with lever arms 422 oriented in a directionopposite to that of the guide sleeve 204 described above. In particular,the lever arms 422 can be oriented such that the tabs 420 configured toengage the body 406 are disposed at a distal end of the lever arms. Thegroove(s) 438 formed in the body 406 in which the tabs 420 are receivedcan likewise be formed more towards the distal end of the stem portion428. The driver instrument 400 can also omit the preload assembly, whichcan reduce the complexity and cost of the instrument. As shown, therelease button 444 is configured to engage the driver shaft 402directly, with the collar and preload spring being omitted.

The instruments disclosed herein can be constructed from any of avariety of known materials. Exemplary materials include those which aresuitable for use in surgical applications, including metals such asstainless steel, polymers such as PEEK, ceramics, carbon fiber, and soforth. The various components of the instruments disclosed herein can berigid or flexible. One or more components or portions of the instrumentcan be formed from a radiopaque material to facilitate visualizationunder fluoroscopy and other imaging techniques, or from a radiolucentmaterial so as not to interfere with visualization of other structures.Exemplary radiolucent materials include carbon fiber and high-strengthpolymers. The devices disclosed herein can also be compatible withimage-guide surgical systems and with stimulation systems (e.g.,neuromonitoring systems typically used to monitor for pedicle breach andto confirm screw or instrument placement).

The devices and methods disclosed herein can be used inminimally-invasive surgery and/or open surgery. While the devices andmethods disclosed herein are generally described in the context ofadvancing a bone anchor assembly into a bone such as the pedicle orlateral mass of a human spine, it will be appreciated that the methodsand devices disclosed herein can be used with any human or animal bone,implant, non-living object, and so forth.

Although the invention has been described by reference to specificembodiments, it should be understood that numerous changes may be madewithin the spirit and scope of the inventive concepts described.Accordingly, it is intended that the invention not be limited to thedescribed embodiments, but that it have the full scope defined by thelanguage of the following claims.

The invention claimed is:
 1. An instrument for driving a bone anchorassembly into bone, the instrument comprising: a driver shaft having adistal drive tip and a proximal driven end; an elongate body havingproximal and distal ends that define a central passage in which thedriver shaft is rotatably disposed, a proximal portion of the elongatebody having a faceted sidewall that includes a plurality of throughholesformed in a single face of the faceted sidewall; and a release buttondisposed in one of the plurality of throughholes of the body and havingat least a first position in which the driver shaft can be completelyremoved from the body and a second position in which the driver shaftcannot be removed from the body; wherein the release button preventscomplete removal of the driver shaft from a proximal-most end of theelongate body when the release button is in the second position; andwherein the release button moves relative to the driver shaft to makethe driver shaft completely removable from the proximal-most end of theelongate body when the release button is in the first position.
 2. Theinstrument of claim 1, further comprising a preload assembly configuredto bias the driver shaft in a distal direction relative to the body. 3.The instrument of claim 2, wherein a location at which the preloadassembly engages the driver shaft can be selected from amongst aplurality of locations to adjust the degree to which the driver shaftprotrudes from the distal end of the body.
 4. The instrument of claim 3,wherein the plurality of locations are defined by radial projectionsthat extend from the driver shaft.
 5. The instrument of claim 2, whereinthe preload assembly is coupled directly to the release button.
 6. Theinstrument of claim 1, further comprising a guide sleeve positionableover the distal end of the body and configured to separate the body andthe driver shaft from surrounding tissue when the instrument is used todrive the bone anchor assembly into the bone.
 7. The instrument of claim6, wherein the sleeve has a flared distal end and a flared proximal end.8. The instrument of claim 6, wherein the sleeve includes a leverconfigured to pivot at a fulcrum point to selectively engage anddisengage the sleeve with the body.
 9. The instrument of claim 8,wherein the lever is formed integrally with the sleeve at a livinghinge.
 10. The instrument of claim 6, wherein the sleeve is rotatablewith respect to the body and with respect to the driver shaft.
 11. Theinstrument of claim 6, wherein the sleeve is configured to engage any ofa plurality of mating features spaced longitudinally along the body. 12.The instrument of claim 1, wherein the body includes an engagementportion formed at a distal end thereof, the engagement portion beingconfigured to engage a corresponding engagement portion on the boneanchor assembly.
 13. The instrument of claim 1, wherein the plurality ofthroughholes allow fluid to access the central passage.
 14. Theinstrument of claim 1, wherein the release button includes a cylindricalrecess in which a sliding collar is disposed, the sliding collar beingmovable relative to the driver shaft.
 15. The instrument of claim 14,wherein the sliding collar includes a plurality of openings spaced abouta sidewall thereof.
 16. The instrument of claim 14, further comprising apreload spring disposed between the collar and the release button. 17.The instrument of claim 16, wherein the preload spring is configured tomove with the release button in a direction transverse to a longitudinalaxis of the driver shaft.
 18. The instrument of claim 14, wherein thesliding collar is configured to move with the release button in adirection transverse to a longitudinal axis of the driver shaft.
 19. Theinstrument of claim 1, wherein the driver shaft can be removed from theproximal end of the body.
 20. The instrument of claim 1, wherein therelease button is configured to move in a direction transverse to alongitudinal axis of the driver shaft when transitioning from the firstposition to the second position.
 21. The instrument of claim 1, whereinthe release button is disposed distal to at least one of the pluralityof throughholes.
 22. An instrument for driving a bone anchor assemblyinto bone, the instrument comprising: a driver shaft having a distaldrive tip and a proximal driven end; a monolithic elongate body havingproximal and distal ends that define a central passage in which thedriver shaft is rotatably disposed; and a release button disposed in thebody and having at least a first position in which the driver shaft canbe removed from the body and a second position in which the driver shaftcannot be removed from the body; wherein the elongate body includes aplurality of throughholes formed in a first face of a faceted sidewallof the elongate body, the release button being disposed distal to atleast one of the plurality of throughholes.
 23. The instrument of claim22, wherein the elongate body includes at least one longitudinal grooveformed between adjacent faces of the sidewall.
 24. The instrument ofclaim 22, wherein a throughhole formed in a second face of the facetedsidewall is substantially aligned with one of the plurality ofthroughholes formed in the first face such that a crossbar can be passedthrough the throughholes of the first face and the second face to createa T-shaped structure for applying additional torque through the elongatebody.
 25. An instrument for driving a bone anchor assembly into bone,the instrument comprising: a driver shaft having a distal drive tip anda proximal driven end; an elongate body having proximal and distal endsthat define a central passage in which the driver shaft is rotatablydisposed; and a release button disposed in the body and having at leasta first activated position in which the driver shaft can be removed fromthe body and a second position in which the driver shaft cannot beremoved from the body; wherein the release button includes a cylindricalrecess in which a sliding collar is disposed, the sliding collar beingmovable relative to the driver shaft; wherein the sliding collar isconfigured to move with the release button in a direction transverse toa longitudinal axis of the driver shaft; and wherein the driver shaftpasses through the sliding collar, and the sliding collar preventsremoval of the driver shaft when the release button is not activated.